1. Field of the Invention
The present invention relates to an integrated reactor missile shield and crane assembly.
2. Description of the Related Art
Pressure vessels containing fuel assemblies in commercial nuclear reactor facilities, such as pressurized water reactors (PWRs), have control rods which are operated by control rod drive mechanism assemblies (CRDMs). The CRDMs are mechanically supported on a removable closure head bolted to the pressure vessel and laterally supported by a seismic support platform and vertically restrained by a missile shield. Missile shields are generally relatively large heavy concrete or metal structures designed to absorb kinetic energy from dislocated CRDMs or other objects originally attached to the reactor pressure vessel.
Each of these components is typically designed and installed as a permanent fixture to perform designated functions during plant operation. However, during refueling of the reactor, the closure head, CRDM assemblies and their supporting subsystems, missile shield and other devices located over the closure head must be disassembled and moved in order to remove the reactor vessel closure head from the reactor vessel.
Typically, as the missile shields and other components are heavy loads, their rigging and handling is a time consuming process and requires use of the reactor building polar crane. Disassembling and moving the missile shields is a complex and potentially dangerous undertaking; many industry events (mishaps) have occurred during missile shield handling.
Numerous missile shield designs have been installed to improve efficiencies and accommodate the various nuclear power plant configurations. One such design provides a missile shield that is a hinged steel structure, and which is rotated clear of the reactor. In another such design, the missile shield rolls along the rails used by the fuel handling bridge (FHB).
At some nuclear power plants, a rolling missile shield would not be practical on the FHB rails, which are crossed by many CRDM cables, head vents, and component cooling water (CCW) piping. At the FHB elevation, a rolling missile shield would interfere with extensive CRDM activities that are routine for such a nuclear power plant.